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Biomedical subjects

L Yardley

Publications and source records attributed to L Yardley.

17 recordsLinked to original sources
PubMed1996

Visually and posturally mediated tilt illusion in Parkinson's disease and in labyrinthine defective subjects.

We tested 24 normal subjects, 24 patients with idiopathic Parkinson's disease (PD), and eight patients with bilateral absence of vestibular function (labyrinthine defective [LD] subjects) in their ability to set a straight line to the perceived gravitational vertical (visual vertical). Measurements were taken in static conditions, sitting upright, and lying down on the right side, and during visual background motion at constant angular velocities around the line of sight (roll-motion) in both sitting upright and sideways position. Aims of the study were to determine if the reported increased "visual dependence" in PD was present in a psychophysical task that is independent of motor performance, and to examine the interaction between visual motion and proprioceptive cues in the perception of verticality, in the absence of vestibular function. LD patients showed abnormally large deviations of the visual vertical induced both by lateral body tilt and by visual roll-motion. This suggests that vestibular cues play a significant part in counterbalancing visually and proprioceptive mediated biases on the perception of verticality. In contrast, PD patients were normal in all these tasks indicating that visual dependence in PD is not present at an afferent/perceptual level.

Adult↗
PubMed1995

Relationship between balance system function and agoraphobic avoidance.

There is a striking similarity between the situations avoided by people with agoraphobia and the environments which provoke disorientation in people with organic balance disorders. This study investigated the possibility that agoraphobia might be linked to balance system dysfunction by comparing the results of balance system tests in 36 people with symptoms of panic and agoraphobia and 20 normal controls. A traditional battery of audiovestibular tests was supplemented with moving platform posturography, which assesses the postural instability induced by disorienting perceptual conditions. Subjects also completed questionnaire measures of somatic symptoms of dizziness and anxiety, agoraphobic cognitions, avoidance behaviour and state anxiety. Over 60% of the Ss with symptoms of panic and agoraphobia were destabilised by the disorienting perceptual conditions, compared with just 10% of the normal controls. Postural instability was strongly related to reported agoraphobic avoidance (r = 0.63, P < 0.01), even after controlling for symptoms, anxiety and agoraphobic cognitions. In our discussion we consider alternative interpretations of these findings, future directions for research, and implications for therapy.

Adult↗
PubMed1995

Effects of anxiety arousal and mental stress on the vestibulo-ocular reflex.

Although the subjective reports of patients suggest that anxiety may aggravate vertigo and imbalance, there has been little research into how anxiety might directly affect balance system functioning. We conducted two studies to examine the effect of anxiety and arousal on the vestibulo-ocular reflex (VOR). In the first study, pre-lest fear ratings were obtained from 20 normal subjects and 36 anxious subjects immediately prior to rotation and caloric testing. Fear ratings were significantly correlated with the maximum slow-phase velocity (SPV) of nystagmus induced by caloric testing. In the second study, we assessed the VOR response to rotation of 36 normal subjects under 3 task conditions: a) minimal alerting (counting backwards during rotation), b) physical arousal (induced by exertion prior to rotation); c) mental arousal (induced by performance of stressful mental tasks during rotation). Both the physical and mental tasks induced a significant increase in heart rate compared with the alerting condition. The maximum SPV of the nystagmus induced by rotation was significantly greater during performance of the mental task than in the other two conditions. These combined results indicate that anxiety may influence the gain of the VOR.

Adolescent↗
PubMed1994

Prediction of handicap and emotional distress in patients with recurrent vertigo: symptoms, coping strategies, control beliefs and reciprocal causation.

Factors predicting handicap and distress were examined in a longitudinal study of 101 patients suffering from recurrent vertigo (dizziness). Analysis of a questionnaire assessing coping strategies yielded four distinct individualised coping styles: problem-focused information-seeking; distraction; denial; and relinquishing responsibility. After controlling for the severity of physical and psychological symptoms and distress, handicap was negatively related to internal locus of control and positively correlated with relinquishing responsibility. Symptoms of somatic anxiety predicted an increase in handicap over a 7 month period, while handicap and somatic anxiety symptoms predicted an increase in distress. These results are interpreted in terms of a reciprocal causal relationship between handicap and distress, mediated partly by somatic symptoms. Parallels with pain, panic and phobia suggest that patients with vertigo might benefit from psychological therapies.

Adaptation, Psychological↗
PubMed1994

A longitudinal study of symptoms, anxiety and subjective well-being in patients with vertigo.

In a prospective longitudinal study of the relationship between symptoms and anxiety in people with vertigo, 101 patients were evaluated on two occasions separated by a 7 month interval. At Time 1 the age, gender, vertigo type, duration of illness, medication, and audiovestibular test results of patients were recorded, and they completed questionnaires assessing handicap, emotional distress, predisposition to anxiety, and symptoms indicative of vertigo and of somatic anxiety. These questionnaires were re-administered at Time 2, and patients also indicated whether their vertigo was more or less severe than at Time 1. Although vertiginous symptoms at Time 2 were generally mild and intermittent, they were associated with significant handicap. Reported symptoms of somatic anxiety and arousal at Time 1 proved to be the only longitudinal predictors of perceived change in vertigo severity over the 7 month period.

Anxiety↗
PubMed1994

Contribution of symptoms and beliefs to handicap in people with vertigo: a longitudinal study.

The purpose of the present study of people with recurrent vertigo (dizziness/dysequilibrium) was (a) to determine whether negative perceptions of symptoms contribute to handicap, and (b) to examine the physical and psychological factors predicting handicap over a seven-month period. Questionnaires assessing symptoms, anxiety and depression, handicap, and beliefs about the potential consequences of vertigo attacks were completed by 101 patients suffering from vestibular disorders. Three clusters of beliefs were identified: concern about loss of control, fear of serious illness, and anticipation of a severe attack. Fear of losing control and reported autonomic symptoms were significantly related to raw and residualized handicap scores, after controlling for somatization, vertigo severity, anxiety and depression. Initial levels of somatization predicted residualized handicap and emotional distress, while handicap levels predicted future emotional distress and vertigo. Negative perceptions of symptoms may contribute to an escalating cycle of vertigo, anxiety and restriction of activity.

Adaptation, Psychological↗
PubMed1992

Symptoms, anxiety and handicap in dizzy patients: development of the vertigo symptom scale.

Questionnaires assessing symptoms, anxiety and handicap were completed by 127 vertiginous patients. Factor analysis identified four distinct symptom clusters which formed the basis for the construction of scales quantifying the number and frequency of symptoms of: (a) vertigo (of long and short duration); (b) autonomic sensations and anxiety arousal; and (c) somatization. Scores on the vertigo severity scale were significantly related to clinical diagnosis and had near-zero correlations with measures of anxiety. Vertigo severity, autonomic signs and depressed mood each independently contributed to variance in handicap, taking precedence over the relationship between handicap and trait and state anxiety. Our findings suggest that the familiar association between anxiety and vertigo may be mediated principally by autonomic symptomatology arising as a result of somatopsychic and psychosomatic processes.

Adolescent↗
PubMed1992

Quantitative analysis of factors contributing to handicap and distress in vertiginous patients: a questionnaire study.

Statements encapsulating common beliefs, behaviour and difficulties associated with vertigo, derived from in-depth interviews, were used to construct a Vertigo Handicap Questionnaire (VHQ) which was completed by 84 patients referred for vestibular testing. Factor analysis identified four principal components of handicap in addition to 'Anxiety and Depression', (which was isolated prior to analysis): 'Restriction of Activities', both physical and social; concern that vertigo would adversely affect social relationships ('Social Anxieties'); 'Fear of Vertigo', both the attacks themselves and their possible significance; and 'Severity of Attacks' which was multiplied with frequency of attacks to give a measure of reported physical disability. Multiple regression revealed that Severity x Frequency of attacks contributed to patient distress only indirectly, through its influence on the mediating psychological and behavioural variables. Significant patient benefit may therefore result from counselling or behavioural therapy, whether or not the vertigo itself can be controlled.

Adolescent↗
PubMed1992

Motion sickness and perception: a reappraisal of the sensory conflict approach.

This review examines the role of activity and perceptual learning in motion sickness by means of a survey of the two kinds of recent research relevant to this topic. The first is a body of literature concerned not with motion sickness as such, but with perception of orientation and self-motion under the conditions of 'sensory conflict' which are thought to provoke motion sickness. The second consists of investigations into the prediction and prevention of motion sickness itself. A major weakness is identified in the methodologies employed in both types of research: namely, a neglect of the way in which responses to unusual and disorienting environments, whether nauseogenic or not, may be affected by the activities, skills and strategies of the perceiver. New directions are outlined for future research into immediate reactions and longer-term adaptation to such environments.

Female↗
PubMed1992

Visual destabilisation of posture in normal subjects.

A new and simple method of assessing reliance on vision for postural control was evaluated in 41 normal subjects. Left-right reversal of peripheral vision induced by a head-mounted mirror device caused an initial dramatic instability in approximately half the subjects, when standing on foam to reduce the value of proprioception. Lateral reversal of central vision by means of a prism device evoked similar responses. Sensitivity to vision reversal was significantly correlated with motion sickness susceptibility. Despite some rapid habituation (partially retained over several weeks) sway remained as great as with eye closure in the anterior-posterior as well as lateral direction, indicating complete suppression of the visual input. Balancing with vision reversal caused a selective decrement in performance of a visuo-spatial memory task, suggesting that coping with misleading visual input may place continuous demands on cortical spatial processing.

Adult↗
PubMed1992

Somatic and psychological factors contributing to handicap in people with vertigo.

Questionnaires assessing symptoms, disability and handicap, predisposition to anxiety, and current anxiety and depression were completed by 127 people attending neuro-otology clinics with a major complaint of vertigo or dysequilibrium. Definite signs of vestibular dysfunction (spontaneous or positional nystagmus, or canal paresis) were found in 56% of the sample, but the presence or absence of abnormal vestibular test results was unrelated to diagnosis, reported symptoms, handicap and psychological status. Two-thirds of employed respondents admitted to occupational difficulties, and more than one in seven had left work because of vertigo. Although the number of people in the sample with a predisposition to anxiety was not unusually high, over a third of the sample had abnormally elevated levels of current anxiety. Multiple regression analyses indicated that disability was determined mainly by physical factors (vertigo severity and duration, age and sex). Handicap was influenced by a mixture of somatic and psychological variables, including the severity of autonomic symptoms. Anxiety and depression were only indirectly related to the severity and duration of the vertigo, insofar as this contributed to handicap. The partial dissociation between these different aspects of patient well-being suggests a need for separate evaluation and differing management of problems at each level of functioning.

Adaptation, Psychological↗
PubMed1991

Orientation perception, motion sickness and vertigo: beyond the sensory conflict approach.

Current theoretical issues central to the understanding of pathological disorientation (vertigo) are addressed through a critical review of research into perceptual disorientation in healthy subjects (motion sickness). Investigations inspired by the 'sensory conflict' model of orientation perception typically paid insufficient attention to higher-order meaningful properties of the environment, purposive activity, and individual differences in sensorimotor experience and skill. These factors are incorporated into an alternative 'active perception' approach, which characterizes perception of orientation as arising from interactions between intra-individual variables and the perceptual properties and sensorimotor demands of the environments encountered. It follows that vertigo is a form of disability which can only be properly assessed in the broader context of a range of relevant attributes of the patient, and his or her activities and environment. Analysis of the principles governing responses to disorienting conditions identifies several factors relevant to the assessment and rehabilitation of vertiginous patients.

Female↗
PubMed1990

Motion sickness susceptibility and the utilisation of visual and otolithic information for orientation.

Movement of large portions of the visual field can induce a static observer to experience illusory self-motion, changes in perceived orientation and motion sickness. Two experiments were performed to determine whether susceptibility to motion sickness might be related to an inability to ignore misleading visual information for orientation, measured here in terms of the magnitude of the apparent tilt of the vertical induced by rotation of the visual field about the line of sight. Significant and additive effects of sex and motion sickness susceptibility were demonstrated. Females susceptible to motion sickness proved highly inaccurate when attempting to set a line to the vertical with rotation of the background, while males resistant to motion sickness were the most accurate at this task. Two possible explanations are discussed, the first suggesting subclinical intersubject differences in otolithic sensitivity, and the second postulating deficiencies in intersensory integration. Parallels are drawn with the patterns of multisensory coordination for postural orientation seen in children and in patients with benign paroxysmal positional vertigo.

Adult↗
PubMed1990

Contribution of somatosensory information to perception of the visual vertical with body tilt and rotating visual field.

This study was designed to explore the role of somatosensory information from the trunk in the perception of the visual vertical. Twelve normal subjects and 1 subject with no somatosensory function below the neck attempted to set a line to the true vertical in the sitting and lying positions, first with a static visual background and then with rotation of the background about the line of sight. The absence of somatosensory information did not affect accuracy when the subjects were in the upright position. When lying horizontally, all control subjects experienced a substantial perceived tilt of the vertical in the direction of body tilt (the A effect), but, in contrast, the subject lacking somatosensory function exhibited a small but consistent apparent tilt of the vertical in the opposite direction (the E effect). This finding is discussed in relation to two competing hypotheses regarding the mechanisms subserving apparent displacement of the subjective vertical in tilted subjects.

Adolescent↗
PubMed1987

The objective estimation of loudness discomfort level using auditory brainstem evoked responses.

The loudness discomfort level (LDL) is of importance in the fitting of hearing aids, but very young children are unable to provide a subjective judgement of LDL. Therefore the relationship between Jewett wave V latency and subjective loudness was investigated to ascertain if objective estimation of LDL is possible. ABR recordings were taken from 8 normally hearing subjects at the stimulus intensity corresponding to their LDL and at stimulus levels from 10 to 30 dB below this. The wave V latency/intensity function did not correlate well with the LDL. However, the slope of this function did correlate to a high degree and a predictive model of LDL was derived. Identical measurements were then taken from a sample of 12 cochlear-impaired subjects with a range of audiometric profiles. Their subjective LDLs could be predicted from the wave V latency function to an accuracy of +/- 5 dB, using the model derived from the normally-hearing subjects. This model appeared to be equally valid for all the degrees and profiles of hearing loss included in the sample and showed a closer relationship to LDL than did absolute wave V latency or estimates derived from the acoustic reflex.

Adult↗